Airplane control system



Sept. 23, 1952 w, Ross 2,611,563

AIRPLANE CONTROL SYSTEM Filed NOV. 28, 1947 Tflna m a;

" INVENTOR.

FREDERICK A TKO/PNEV' Patented Sept. 23, 1952 STATE 3' P,ATE

NT! Fl- B5} This invention relates, to airplanes, and more particularly to aerodynamic control, systems therefor including roll, yaw, and pitch controls which'have characteristics that reduce theskill required to pilot an airplane and that reduce the dangers'of piloting an airplane.

All airplanes, inorder to be maneuvered while flying in the. air and during take-off and landing,

have devices-to control the. angular position of the airplanewithrespect to the surrounding-air and the ground, These devices are known collectively in'the art. as the aerodynamiccontrol pitch control, such as an elevator, to control the pitch angle or angle of attack ofthe airplan with respect to the oncoming air. y In maneuvering an airplane by these aerodynamic controls inconjunction with the engine controls, it is necessary for the pilot-to coordinateproperly theamount of and the time of application ofeachcontrol during each instant of each maneuver. of the roll control with the yaw control, which is necessary in" order tov perform a true-banked or properly coordinated turn, requires considerable skill and much practice on the part of the pilot, is difiicult to master, and has been a source of danger, the pilot often failing to coordinate properly at'a time when the dangers of a spin are imminent. The incident invention aims to improve the characteristics of the aerodynamic control system referred to so as to reduce the pilot skill required, to reduce the time required to learn to pilot, and to reduce the dangers of piloting an airplane. 1

An object of the invention is to provide an aerodynamic control system with improved means for automatic coordination of the roll control with the yaw control.

Another object of the invention is to provide an aerodynamic control system, with improved means for operating the roll control in combination with the yaw controlbya single control lever. Another object of the invention is-to provide an aerodynamic control system with means for automatic coordination of the roll con-trol withplane improved performance.

In particular, the coordination '2 Claims. (01. 244-83) Other objects and advantages of the invention I will appear from the following description when considered in connection with the drawings forming a part of this specification, and in which:

i Fig. 1 is a perspective viewof an airplane illustrating the control system as installed. H V

Fig. 2 is a perspective view of the-controlsystem partly broken away, and r V Fig. 3 isa fragmentary top plan view.

Referring to the drawings for more specific details of the invention 10 represents a fuselage having suitable housing facilities for a pilot and passengers, and also suitable housing for a power plant, not shown, for driving a propeller I2. The fuselage also carries conventional empennage l4.

Oppositely disposed wings l6 of like structure are secured to thefuselage, and ailerons lii are hinged to the trailing edges thereof and the wings,

support a main landing gear, not shown, prefe'r-'- ably of the retractable type.

The empennage 14 consists of a conventional fixed horizontal stabilizer 20 with oppositely disposed corresponding elevator surfaces 22 hinged to the trailing edge thereof, and a fixed vertical fin 24 with a rudder 2B hinged to. its

' dependent arm 34, the purpose of which will hereinafter appear.

An arm 36 fixedly secured on the torque tube 28 is connected by a link 38 to one arm of a bell crank. mounted on a fixed pivot 42, and the other arm ofthe bell crank is connected by a push-- pull rod 44 toa horn 46 on the rudder 26, and the I dependent arm 34 of the control stick 3!! is con nected as by a push-pull rod 48 to horns 50 on the elevators 22.

An arm 52 fixedly secured to the control stick I 30 at a suitable elevationabove the pivot 32 ofthe stick is pivotally connected as at 54 to one end of a link 56 the other end of which is connected to one arm of a bell crank 58 mounted on a fixed pivot 60, and the other arm of the bellcrank 58 is connected by push-pull rods 62to-; bell cranks 64 mounted on fixedpivots 66 and connected in turn bylinks 68 to horns 10 on the ailerons I 8.

The control system isoperative in the following manner: when the airplane is being maneuvered for a turn to the right, for. example, the control stick 30 is movedto the right. This movement of the stick rotates the torque tube 28 and transmits force through the arm 35, the link 88, the bell crank 40, the push-pull rod 44 and the horn 45 to deflect the rudder 26 with its trailing edge to the right of its normal position. This 4 of fixed length between the pivot 60 and the connection of the bell crank 58 and push-pull rods 62, and a lever arm of variable length between pivot 60 and. the pivot 54. The lateral motion movement of the rudder impresses a turning 5 of pivot 54 as described hereinbefore, causes an moment on the airplane, yawing its nose to the right.

Simultaneously with this rudder movement, force is tfansmitteidlthrough the arm. 52 on the.

opposite lateral motion of push-pull rods 62, the proportion of lateral motion being determined by the particular fore or aft position of pivot 54 with. respect to'axis 60:.(as described hereinbecontrol stick,the link 56, the bell crank 58, the fore)- push-pull rods 62, the bell cranks 64, the links 68 and the horns F0 on the ailerons, so that theright aileron trailing edge is moved upfrom its. 7

normal position and the left aileron trailing edge The control system in this way provides a means whereby the proportion of roll control momentto. yaw control moment is variable and is determinedby'the position of the elevator conis moved down. This aileron movement iml5:l -Thi5 ys m Provides means by With presses a rolling moment on theairPIane causing;

it to roll with the right side low and banking the airplane for a turn to the right. Movement of the control stick aft rotates the stiekrabout-pin'fizl This movement-of the-stick greater angles transmits force through-the dependent arm 34,-. thepush-pull rodq48, and the horn 5E3 to .roetate the elevator .:2Z,- raisingythetrailing edge thereof, During flight this elevator movement lowers the 'tail1.of;the airplane and hence in creases theangle .of. attack .otthe airplane. Since the lift of the :wings 16 is greaterfo'ra greater angle. ofattack and .is...less er for a lower speed, then for normal viiightconditions the angle oiattack is. greaterfor lower airplane speed.

Also, during. all. maneuvers. involving a turn, thelift .on the .wing must be increased by. his creasing ,the angle ,oi attack. .50 .as. .to provide centripetal .force .for performinggthe. turn. Dursa single pilots control lever, a greater amount of yaw control is simultaneously obtained along Withia particular amount of roll control for elevator or pitch control settings corresponding to Hence the system comprises aninterconnected roll control. and yaw control which provides greater yaw control at: lower airspeeds where"the. angle -of attack iis" higher."

The greater proportion'of yaw controlth'us' ob tained at higher angles 'ofattack, provide'sla means for "essentially eliminating the effects'oL the greater adverse yaw "whichcccurs' at "the": higher angles "of -attack withapplic'ation of "a7.

5-particular amount of roll control; and makes it' possible to perform bankedtu'rns with the air: plane which closely approximate true-banked turns by using'only a single control lever.

In performing a complete turn to the right'witli ing., alllfflight maneuvers thenithe ..angle..of.,'atthe control system of #5119 incident"mi/"animate" tack isxcontrollerl by. the positionof the, elevatorv throughthe fore and aftpositionof the control I stick; For. low-angles of attack thecontrol. stick. 30 is'held in" a forward position, and for increase described herein'befo're, the control" stick" is pressed to the right 'until'the desired bank ises tablished' and is pressed slightly aft to account for the increasedcentripetalforce needed toper-' ing angles of attack the control stick is held in 40 form the turn- Afterthe bank is established,

correspondinglyv farther aft positions,

This definite relationbetween the control stick position and angle of attack vmaybe slightly modified an unimportant amount by. extraneous the control stick'30 is returned approximately to neutral laterallyfth'e' slight aft shift 'inposition being held. The stick 3!] is held in-this position until it is desired to recover from the turn.- For efl'e' ts' ugha by the influe of the propeller the-recoverytheoperations are-reversed with slip streamon the elevator. The latter introdu'ces "IlOflIIlPOItBiIlt influence on the operation especially for airplanes which have the .rudder. in the slipstream where the change in effectivethe controlstick'being-returned finally to thew original positi'on1priorto the start of the turn;

Turns to the leftare performed by using left" hand motion-ofthe stick in place'oif right hand ness of the rudder compensates for the change and 'vic'eversa:

in eiiectiveness of the elevator.

The linkage'connecting the control stick to the ailerons is arranged so that the angular defiec tion of the ailerons for a particular amount of With this system of aerodynamic control then"- the pilot need not perform the diflicult coordi nation of hand operated aileron control with'ai separate foot operated 'rudderco'ntroh as must lateral displacement 'of the control" stick, is be done with the conventional three-controlsysgreaterior 'the more forward pitch'isettings oft" the "control stick and is lesser for the. more aft settings. This is illustrated in Figs.'2 and 3.'

Lateral motion of the control stick also moves tem as used on nearly all airplanes prior to this invention.

This coordination of separate rudder and ailer on controls is performed through observation of the arm-52 laterally. This results in the trans- 0 tipping (in roll) by the pilot as he sits in the seat,

mission of force through an adjuster, comprising the link 56 and the bell crank 58, the push-pull rods '62, the bell cranks 64, and'the links 68 to the horns H3 on the ailerons It. The link 55 can and can be learned and acquired only after many hours of practice; In addition, since the observation of this tipping is ratherdifiicult to detect it'may passlunobs'erved during times of stress rotate about its connections at each end. When when the pilot is in "danger as when near the,

the control stick is in a more forward position the arm 52 fastened to the control stick '30 also is in *a more forward position and the pivot 54 is-closer to the fixed pivot 68.. Likewise aft pogrouncl during landing or take-oil and whenhe is' flying the airplane near the stalling speedarUnder these conditionsan inadvertentrstall andim-E. proper co'ordination'can lead to a spin and con-.

sitions of the control stick introduce correspond- 70 quent crash."

ingly greater separations of pivot 54 and the fixed pivot 60.

The linkage'connecting the arm 52 to the ailerons l 8 arranged ias described provides, in ef-' With the'controlsystem of the incident invention the pilot need not learn the coordination of separate rudder .and aileron controls, and hence. the ,diific'ulties of" learning: to fly. are greatly refeet; a lever with pivot at axis 60, and a lever arm diiced; The dangers f impr per coordinatioh-.-,

are also eliminated, since the coordination is performed automatically by the control system.

The control system of the incident invention is an improvement over existing control systems which do not require coordination of the aileron and rudder control. Control systems of this type are referred to in the art as the two-control type as contrasted to the three-control type which have independent aileron and rudder control in addition to the independent elevator control.

Existing two-control types are of two kinds. In one kind, the airplane is designed to have comparatively high directional stability and with ailerons having comparatively low adverse yaw. For this kind of two-control system the adverse yaw is also greater for lower speeds than for higher speeds and consequently turns at speeds near the stall are not properly banked. For the second kind of two-control system in existence prior to this invention, the aileron and rudder are actuated by a single control lever. The ratio of roll control to yaw control, however, is constant so that the proportion of roll to yaw obtained is only correct for turns at one particular angle of attack. Consequently for turns made at all other angles of attack, the airplane slips or skids. The proportion of roll control to yaw control is usually selected for the lower angles of attack corresponding to higher speeds. Hence, for the higher angles of attack at lower speeds there is not adequate yaw control in proportion to the roll control to take care of the greater adverse yawing tendencies of the roll control at the lower speeds.

With the incident invention the ratio of yaw control moment to roll control moment, which is obtained by a single control lever motion is regulated by the pitch control setting which also controls the angle of attack. Hence, this invention automatically regulates the ratio of yaw control moment to roll control moment to take care of the increased adverse yawing tendencies of the roll control at lower speeds.

Consequently, with the incident invention good coordinated turns can be made at all speeds down to the stall speed. It is not necessary to restrict the pitch control to avoid the diificulties experienced with prior control systems of the "two-control type at low speed near the stall. With the incident invention a useful lower speed and hence a better performance is obtained.

While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art.

Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:

1. In an aircraft, having a wing mounted thereon, an aerodynamic control system for the aircraft comprising a roll element mounted on the wing, a yaw element, and a pitch element, a control member pivotally mounted for rotation about two non-parallel axes, means interconnecting the control member to the pitch element to provide deflection thereof upon actuation of the control member about the first of its axes of rotation, means interconnecting the roll and yaw elements, said last mentioned means including a rockable member pivoted on fixed aircraft structure on an axis spaced with respect to the control member and in a plane perpendicular to said first axis, and means connected at one end to the control member at a point spaced from its first axis of rotation and at its other end to the rockable member at a point spaced laterally from said perpendicular plane.

2. In an aircraft an aerodynamic control system therefor comprising roll, yaw, and pitch elements, a control member mounted for rotation about two non-parallel axes, means interconnecting the control member to the pitch element to provide deflection thereof upon. actuation of the control member about the first of its axes of rotation, means interconnecting the control member to the yaw element to provide deflection thereof upon actuation of the control member about the second of its said axis of rotation, means interconnecting the control member to the roll element to provide deflection thereof upon actuation of the control member about the second of its said axes of rotation, said last mentioned means including an adjustor means operably interconnected to the pitch element, said adjustor means to adjust the ratio of transmission of deflection of the control member to defiection of the roll element, said ratio of transmission being determined through the interconnection of the adjustor means to the pitch element by the positioning of the pitch element.

FREDERICK W. ROSS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,830,429 Elsby NOV. 3, 1931 2,276,702 Riparbelli et al. Mar. 17, 1942 2,478,033 Weick "Aug. 2, 1949 FOREIGN PATENTS Number Country Date 323,881 Germany Aug. 11, 1920 

